Such an arrangement comprises a flap that forms an integral part of the instrument panel, having its outline delimited by a precut line made on the underside face of the instrument panel, so that this flap is not visible to an occupant of the vehicle.
An inflatable airbag module is fixed to the underside face of the instrument panel, in the region of the flap, so that when airbag inflation is triggered, this airbag applies pressure to the underside face of the flap to cause this flap to open by breakage along the precut line. Opening then allows the airbag to deploy into the passenger compartment of the vehicle in order to protect the corresponding occupant.
Such a flap typically has a rectangular outline and is articulated with respect to the rest of the body of the instrument panel at the front transverse edge of its outline, namely the edge closest to the windshield of the vehicle.
In a solution known from document U.S. Pat. No. 5,653,46 and depicted in FIG. 1, the flap, with the general reference 1 is articulated to an instrument panel 2 by means of two tethers referenced 3.
Each tether has an upper end rigidly secured to the underside face of the flap, near the front edge of this flap with respect to the direction of forward travel A of the vehicle, and a lower end which is secured to the instrument panel 2, so that it can slide in relation thereto.
For this purpose, and as can be seen in FIG. 1, each tether 3 is passed through a corresponding tab 4 fixed to the front edge of the opening 6 of the instrument panel which accepts the flap 1. Each tether 3 has the overall form of a band or strap with a lower termination 7 that is wider than the opening delimited by each tab 4, thus forming a stop immobilizing the tether when its termination 7 reaches the tab.
In practice, when airbag inflation is triggered, this causes the opening of the flap which occurs in the form of a combined movement in which the flap lifts in relation to the instrument panel and rotates about the front edge of this flap.
The lifting of the flap in relation to the rest of the instrument panel is made possible by the sliding of the tethers 3 in the tabs 4 in an approximately vertical direction until the terminations 7 of the tethers come into abutment against these tabs 4.
In practice, it is necessary for the flap to be able to lift in relation to the rest of the instrument panel so that it can open with the suitable dynamics, notably without the risk of jamming. However, the setup with sliding tethers as illustrated in FIG. 1 is ill-suited to industrial-scale production as it is too expensive to implement in relation to the prices commanded.
In particular, bearing in mind the significant forces involved when the flap opens, there remains a significant risk that the terminations of the tethers will, nonetheless, pass through the tabs, this resulting in the flap being thrown out into the passenger compartment of the vehicle thereby potentially injuring an occupant.